1. Field of the Invention
Methods and apparatuses consistent with the present invention relate to a digital broadcast reception/transmission system, and more particularly, to a multi-program multiplexing/demultiplexing method and apparatus for preventing MPEG jitters from being generated in digital broadcasts, and a multimedia receiver performing the multi-program multiplexing/demultiplexing method.
2. Description of the Related Art
As digital video/audio compression and digital transmission technologies have been enhanced, digital broadcasts which can provide broadcast services having a higher picture quality, compared to analog broadcasts, and which have high interoperability with digital communication media, digital storage media, etc, have been developed.
In general, a digital broadcast is transmitted in the form of a transport stream encoded based on the MPEG-2 standard.
Recently, the number of broadcast channels has gradually been increasing. Accordingly, a system which can store a plurality of broadcast programs received through a plurality of channels while the programs are being watched is needed. In order to meet the need, broadcast receivers having a Picture In Picture (PIP) function and a double window function are being commercialized.
In general, a cable broadcast system multiplexes programs received through a plurality of channels, and transmits multiplexed transmission streams to a broadcast receiver. At this time, there is a need to minimize Program Clock Reference (PCR) jitters of the multiplexed transmission streams. The PCR is time information for setting a System Time Clock (STC) value of a system decoder to a value suitable for an encoder side.
FIG. 1 is a timing diagram for explaining a related art multi-program multiplexing method which is performed in a related art cable broadcasting system.
Referring to FIG. 1, a plurality of channel decoders (not shown) output a plurality of transport stream packets TS1 to TSn, respectively, according to channel characteristics (for example, their transport stream rates). A Cable Card MPEG Packet (CMP) generator (not shown) adds control information to a transport stream of each channel and generates a CMP. A multiplexer (not shown) then multiplexes CMPs of the respective channels and generates a packet sequence.
The output timing of the multiplexed packet sequence depends on the input order of transport stream packets and the duration of each transport stream packet. However, in the related art multi-program multiplexing method, since uniform time intervals between local transport streams cannot be ensured, MPEG jitters occur. Accordingly, in the related art multi-program multiplexing method, errors occur in clock (27 MHz) locking of an MPEG system, due to such MPEG jitters.